In a data center network, virtualization applications of a server are more widely popular. A physical server may be virtualized into a plurality of virtual machines (VM). By using virtualization technology a data center may provide data escrow and other services for a plurality of different tenants. Tenants may be the resource users of the data center, for example corporations or others that store data and/or applications in the data center. Data escrow is the storage of data by a neutral third party. To ensure the safety of data escrow of tenants, virtual networks may be used to isolate traffic relating to different tenants. Thus, a plurality of virtual networks may be set up over the internal physical network of the data center.
To achieve the object of the internal physical network of the data center being divided into different virtual networks, the existing technology provides the Network Virtualization Over Layer3 (NVO3). NVO3 technology is an overlay technology. By using the channel encapsulation technology, the packet of the virtual network may be performed the channel encapsulation. Thus different virtual networks may be distinguished through a different virtual network identifier. The NVO3 technology may use Media Access Control in Internet Protocol (MAC in IP) channel encapsulation technology. The NVO3 may for example use a 24-bits virtual network identifier, so that the tenants may create isolated virtual network with a maximum number of 16M.